U.S. patent application number 11/037253 was filed with the patent office on 2005-09-22 for device and method for manufacturing carbon nanotube.
This patent application is currently assigned to THE UNIVERSITY OF TOKYO. Invention is credited to Hoshino, Kazunori, Maruyama, Shigeo, Matsumoto, Kiyoshi, Murakami, Yoichi, Shimoyama, Isao.
Application Number | 20050207965 11/037253 |
Document ID | / |
Family ID | 34901269 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050207965 |
Kind Code |
A1 |
Shimoyama, Isao ; et
al. |
September 22, 2005 |
Device and method for manufacturing carbon nanotube
Abstract
There is provided a device for manufacturing carbon nanotube.
The devices has a chamber support part for supporting a chamber
which contains a plurality of microstructures, each of which is
separated from each other by an interval; a gas providing part,
connected to the chamber, for flowing at least one reactant gas,
including raw material gas for manufacturing carbon nanotubes,
through the chamber; a measurement part for measuring a change in
physical properties of at least one of the plurality of
microstructures by using detecting part; and a control part for
controlling the gas providing part based on the measured change in
physical properties.
Inventors: |
Shimoyama, Isao; (Tokyo,
JP) ; Maruyama, Shigeo; (Tokyo, JP) ;
Matsumoto, Kiyoshi; (Tokyo, JP) ; Hoshino,
Kazunori; (Tokyo, JP) ; Murakami, Yoichi;
(Tokyo, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
THE UNIVERSITY OF TOKYO
Tokyo
JP
|
Family ID: |
34901269 |
Appl. No.: |
11/037253 |
Filed: |
January 19, 2005 |
Current U.S.
Class: |
423/447.3 ;
204/164; 422/105 |
Current CPC
Class: |
D01F 9/127 20130101;
B82Y 30/00 20130101 |
Class at
Publication: |
423/447.3 ;
422/105; 204/164 |
International
Class: |
D01F 009/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 23, 2004 |
JP |
2004-15,962 |
Claims
What is claimed is:
1. A method for manufacturing carbon nanotube, the method
comprising the steps of: flowing at least one reactant gas through
at least one reaction region including a plurality of
microstructures, each of which is separated from each other by an
interval, and to generate and grow at least one carbon nanotube
such that a bridge is made between the microstructures; measuring a
change in physical properties of at least one of the plurality of
microstructures by using detecting means; and controlling the
generation and growth of at least one carbon nanotube based on the
measured change in physical properties.
2. The method according to claim 1, wherein the detecting means
includes at least one selected from the group consisting of a force
sensor, an electrical resistance meter, optical lever method
measurement instrument, and a Raman spectrometer.
3. The method according to claim 1, wherein each of the plurality
of microstructures includes at least one minute vibrating
cantilever.
4. The method according to claim 3, further comprising providing
vibration to the minute vibrating cantilever from without by using
an electrostatic actuator or a piezoelectric actuator.
5. The method according to claim 4, wherein there are a plurality
of minute vibrating cantilevers, each having a different resonance
frequency, the method further comprising adjusting a frequency of
the provided vibration from without by the providing vibration step
according to a desired resonance frequency of the minute vibrating
cantilevers.
6. The method according to claim 4, wherein there are an array of
reaction regions, the method further comprising controlling at
least one selected from the group consisting of heating of a
reaction region, flow rate of reactant gas, and electric field for
every reaction region.
7. The method according to claim 6, wherein the heating of a
reaction region done by a spot lamp, which locally heats by
irradiating only a limited part, or a heater having a resistance
heating element.
8. The method according to claim 6, wherein each of reaction
regions included in the array is provided in each of micro flow
channels which are provided in a substrate by MEMS technology.
9. The method according to claim 8, wherein each of the reaction
regions is connected to a plurality of micro flow channels in a
different direction, and wherein the method further comprising
controlling a flow direction of the reactant gas which passes
through the reaction region by adjusting a flow of the reactant gas
for every micro flow channel, and to generate and grow the at least
one carbon nanotube.
10. The method according to claim 1, further comprising the steps
of: determining whether or not each of the generated and grown
carbon nanotubes is a desired one based on the measured change in
physical properties; and burning up only one or more carbon
nanotubes, which are determined that each of which is not desired
one in the determining step, of the generated and grown carbon
nanotubes either by applying electric current to the one or more
non-desired carbon nanotubes via electrodes provided in the
microstructures or by flowing an oxygen gas through the reaction
region in which the one or more non-desired carbon nanotubes are
formed therein.
11. The method according to claim 1, wherein the generation and
growth of the at least one carbon nanotube is done in a
non-oxidizing atmosphere.
12. A device for manufacturing carbon nanotube, comprising: chamber
support means for supporting a chamber which contains a plurality
of microstructures, each of which is separated from each other by
an interval; gas providing means, connected to the chamber, for
flowing at least one reactant gas, including raw material gas for
manufacturing carbon nanotubes, through the chamber; measurement
means for measuring a change in physical properties of at least one
of the plurality of microstructures by using detecting means; and
control means for controlling the gas providing means based on the
measured change in physical properties.
13. The device according to claim 12, further comprising: at least
one heating means for heating the plurality of microstructures in
the chamber; and/or electric field providing means for providing
electric field to the plurality of microstructures in the chamber
via at least one electrode connected to any of the plurality of
microstructures, and wherein the controlling means controls the
heating means and/or the electric field providing means based on
the measured change in physical properties.
14. The device according to claim 12, wherein the detecting means
includes at least one selected from the group consisting of a force
sensor, an electrical resistance meter, optical lever method
measurement instrument, and a Raman spectrometer.
15. The device according to claim 12, wherein each of the plurality
of microstructures includes at least one minute vibrating
cantilever.
16. The device according to claim 12, further comprising: either an
electrostatic actuator or a piezoelectric actuator for providing
vibration to the minute vibrating cantilever from without.
17. The device according to claim 16, wherein there are a plurality
of minute vibrating cantilevers, each having a different resonance
frequency, the device further comprising controlling means for
controlling electrostatic actuator or a piezoelectric actuator to
adjust a frequency of the provided vibration from without according
to a desired resonance frequency of the minute vibrating
cantilevers.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a device and method for
manufacturing carbon nanotube.
[0003] 2. Related Art Statements
[0004] Up to now there have been developed various techniques for
forming carbon nanotubes. However, in any of the techniques, it is
very difficult to know the nature of the generated nanotubes and
correct number of the nanotubes, so that until now there has not
been developed a technique or device for forming nanotubes at
desired locations with the desired number of nanotubes. For
example, as conventional technologies of the nanotube generation,
there have been developed various methods and devices for forming
carbon nanotubes at high temperature (equal to or more than 1000
degrees centigrade). Moreover, there is a technique for generating
nanotubes at low temperature (about 600 degrees centigrade) by
Shigeo Maruyama who is one of the inventors of the present
invention, et al. (Refer to Japanese documents: Maruyama Shigeo,
"Growth of Nanotube by the cold CVD with Alcohol (experiment and
simulation)", Journal of Japanese Association for Crystal Growth
cooperation (2002), Vol. 30, No. 4, pp. 32-41; Shigeo Maruyama,
"Synthetic Technology of the Single Layer Carbon Nanotube with
Alcohol", Industrial material (2003), vol. 51, No. 1, pp. 38-41;
and Shigeo Maruyama et al., "High Purity Generation at low
temperature by Single Layer Carbon Nanotube with Low Temperature
CCVD technique with Alcohol", Journal of Japan Society of
Mechanical Engineers (B part), (2003), vol. 69, No. 680, pp.
918-924.
SUMMARY OF THE INVENTION
[0005] It is an object of the present invention to provide a device
and method for manufacturing carbon nanotube.
[0006] In order to solve the above-mentioned problems in the
conventional devices and methods, there is provided a method for
manufacturing carbon nanotube, the method comprises the steps
of:
[0007] flowing at least one reactant gas through at least one
reaction region including a plurality of microstructures, each of
which is separated from each other by an interval, and to generate
and grow at least one carbon nanotube such that a bridge is made
between the microstructures;
[0008] measuring a change in physical properties (for example, a
minute change in physical properties (e.g., mechanical or optical
physical properties) when a carbon nanotube bridge is built) of at
least one of the plurality of microstructures by using a detecting
means (for example, force sensor which uses a cantilever, or the
like); and
[0009] controlling the generation and growth of at least one carbon
nanotube based on the measured change in physical properties.
[0010] According to the present invention, it is possible to easily
form carbon nanotubes at desired locations with desired number of
nanotubes, because the nanotubes are manufactured while monitoring
the forming of the nanotubes such that number and properties (for
example, electric conductivity or length of a carbon nanotube) of
the nanotubes generated and grown are correctly or precisely
measured by the detecting means. For instance, it is assumed that
one or more detecting means for detecting physical properties are
provided in both or either a microstructure A and a microstructure
B, at which one or more bridges of carbon nanotubes are built
therebetween, desired number of the carbon nanotubes can be formed
while monitoring the growth of the carbon nanotubes by stopping the
generation and growth of the carbon nanotubes if when the number of
the tubes, which have bridged between the microstructures A and B,
reaches to a desired number based on the monitoring result.
According to this invention, manufactured carbon nanotubes can be
applied to various sensors, or various devices (e.g., a field
effect transistor or optical crystal) which use nanotubes, because
carbon nanotubes can be formed and grown at one or more desired
locations with a desired number of tubes.
[0011] In an embodiment of the manufacturing method according to
the present invention, the detecting means includes at least one,
or combination, selected from the group consisting of a force
sensor (e.g., minute vibrating cantilever type force sensor), an
electrical resistance meter, optical lever method measurement
instrument, and a Raman spectrometer.
[0012] According to the present embodiment, when a mechanical
method using force sensor is employed, it is possible to measure
mechanical properties regardless that the generated or formed
carbon nanotubes are electrically conductive or semi-conductors.
Meanwhile, when electric resistance is measured, it is possible to
identify or figure out the number and characteristics of the carbon
nanotubes such that how many semiconductor nanotubes are formed and
that how many nanotubes having electrical conductivity are
generated. Therefore, when changes in a plurality of physical
properties are obtained using these various measurement devices, it
is possible to manufacture desired nanotubes while correctly or
precisely grasping the number and types/kinds (e.g., diameter of a
tube, or electric conductivity, etc.) of the nanotubes.
[0013] In another embodiment of the manufacturing method according
to the present invention, each of the plurality of microstructures
includes at least one minute vibrating cantilever.
[0014] According to the present embodiment, it is possible to
measure the lengths, properties, and the number of the formed
carbon nanotubes with a high degree of accuracy, because the
physical properties of the minute vibrating cantilever slightly
varies depending on the minute stimulus arising from the nanotube
generation (i.e., a nanotube bridge is finished up between the
cantilevers/microstructures).
[0015] Meanwhile, silicone is preferable as a material to form a
cantilever, but at 1000 degrees centigrade, in which normal
nanotube forming method is performed, it is difficult to measure
the mechanical characteristics of the silicone. However, when the
above-described Low Temperature CCVD technique with alcohol by
Maruyama is employed, nanotubes can be formed at low temperature
such as approximately 600 degrees centigrade. This temperature, 600
degrees centigrade, is within the range (it is desirable to be
equal or less than 700 degrees centigrade) of the elastic
deformation of silicone. Therefore, if the Low Temperature CCVD
technique is used, the minute changes in physical properties of the
cantilever may sufficiently be measured. Hence, in this embodiment,
when microstructures having cantilevers made of silicone are
employed, it is preferable that the method includes a step of
controlling temperature of a reaction region, at which the
microstructures having cantilevers exist, to be within the range
from approximately 600 to approximately 700 degrees centigrade.
[0016] In still another embodiment of the manufacturing method
according to the present invention, the method further comprises
providing vibration to the minute vibrating cantilever from without
or from outside of the cantilever by using an electrostatic
actuator or a piezoelectric actuator.
[0017] In yet another embodiment of the manufacturing method
according to the present invention, there are a plurality of minute
vibrating cantilevers, each having a different resonance frequency,
the method further comprises adjusting a frequency of the provided
vibration from without by the providing vibration step according to
a desired resonance frequency of the minute vibrating
cantilevers.
[0018] In yet another embodiment of the manufacturing method
according to the present invention, there are an array of reaction
regions, in other words reaction regions are accumulated on large
scale to form the array, the method further comprises controlling
at least one selected from the group consisting of heating of a
reaction region, flow rate of reactant gas, and electric field for
every reaction region.
[0019] According to the present embodiment, it is possible to
manufacture only the desired number of the nanotubes having desired
properties in a large quantity. For instance, when only certain
reaction regions, at which microstructures exist where one or more
nanotube bridges should be built therebetween, are heated according
to this method, only the certain reaction regions are activated,
and therefore this makes remaining reaction regions to not generate
or form the carbon nanotubes in these remaining non-activated
reaction regions. In addition, due to that electric filed is
applied to spaces between certain microstructures at which one or
more nanotubes bridges should be built therebetween, a direction of
the growth of the nanotubes can be controlled.
[0020] In yet another embodiment of the manufacturing method
according to the present invention, the heating of a reaction
region done by a spot lamp, which locally heats by irradiating only
a limited part of the reaction regions, or a heater having a
resistance heating element.
[0021] In yet another embodiment of the manufacturing method
according to the present invention, each of reaction regions
included in the array is provided in each of micro flow channels
which are provided in a substrate by MEMS (Micro electro mechanical
systems) technology.
[0022] In yet another embodiment of the manufacturing method
according to the present invention, each of the reaction regions is
connected to a plurality of micro flow channels in a different
direction, and the method further comprises controlling a flow
direction of the reactant gas which passes through the reaction
region by adjusting a flow of the reactant gas for every micro flow
channel, and to generate and grow the at least one carbon
nanotube.
[0023] According to this embodiment, it is possible to form and
grow a nanotube in desired direction by flowing reactant gas in the
desired direction through which a nanotube should be formed and
grown, because the nanotube tends to grow according to (i.e., along
with) the flow direction of a reactant gas.
[0024] In yet another embodiment of the manufacturing method
according to the present invention, the method further comprises
the steps of:
[0025] determining whether or not each of the generated and grown
carbon nanotubes is a desired one based on the measured change in
physical properties; and
[0026] burning up only one or more carbon nanotubes, which are
determined that each of which is not desired one in the determining
step, of the generated and grown carbon nanotubes either by
applying electric current to the one or more non-desired carbon
nanotubes via electrodes provided or disposed in the
microstructures or by flowing an oxygen gas through the one or more
reaction regions in which the one or more non-desired carbon
nanotubes are formed therein.
[0027] In yet another embodiment of the manufacturing method
according to the present invention, the generation and growth of
the at least one carbon nanotube is done in or under a
non-oxidizing atmosphere (for example, by flowing an argon gas
containing hydrogen through the reaction regions).
[0028] According to this embodiment, changes in physical properties
such as optical or mechanical characteristics by the oxidation
reaction of the minute structure can be avoided by preventing the
microstructures from being oxidized, so that measurement error of
the change in physical properties can be confined within a minimum
range.
[0029] In an alternative embodiment, the method may further
comprises calculating compensated values regarding mechanical
properties from a temperature and an elapsed time by compensating
the error of change in mechanical properties by oxidative reaction
from heat and oxygen during nanotube forming (surfaces of the
silicone will be converted into oxide silicone by heating).
[0030] By way of easy explanation the aspect of the present
invention has been described as the methods, however it is
understood that the present invention may be realized as devices
corresponding to the methods.
[0031] For example, according to another aspect of the present
invention, there is provided a device for manufacturing carbon
nanotube, the device comprises:
[0032] a chamber support means for supporting a chamber which
contains a plurality of microstructures, each of which is separated
from each other by an interval or distance;
[0033] a gas providing means, connected to the chamber, for flowing
at least one reactant gas, including raw material gas for
manufacturing carbon nanotubes, through the chamber;
[0034] a measurement means for measuring a change in physical
properties of at least one of the plurality of microstructures by
using a detecting means; and
[0035] a control means for controlling the gas providing means
based on the measured change in physical properties.
[0036] In another embodiment of the manufacturing device according
to the present invention, the device further comprises:
[0037] at least one heating means for heating the plurality of
microstructures in the chamber; and/or
[0038] an electric field providing means for providing electric
field to the plurality of microstructures in the chamber via at
least one electrode connected to any of the plurality of
microstructures,
[0039] and the controlling means controls the heating means and/or
the electric field providing means based on the measured change in
physical properties.
[0040] In still another embodiment of the manufacturing device
according to the present invention, the detecting means includes at
least one selected from the group consisting of a force sensor, an
electrical resistance meter, measurement instrument using optical
lever method, and a Raman spectrometer.
[0041] In yet another embodiment of the manufacturing device
according to the present invention, each of the plurality of
microstructures includes at least one minute vibrating cantilever,
i.e., a cantilever which minutely vibrates.
[0042] In yet another embodiment of the manufacturing device
according to the present invention, the device further
comprises:
[0043] either an electrostatic actuator or a piezoelectric actuator
for providing vibration to the minute vibrating cantilever from
without, or outside of the cantilever.
[0044] In yet another embodiment of the manufacturing device
according to the present invention, there are a plurality of minute
vibrating cantilevers, each having a different resonance frequency,
the device further comprises a controlling means for controlling
electrostatic actuator or a piezoelectric actuator to adjust a
frequency of the provided vibration from without, or outside the
cantilever, according to a desired resonance frequency of the
minute vibrating cantilevers.
[0045] In yet another embodiment of the manufacturing device
according to the present invention, the device further comprises a
temperature control means for controlling temperature of a reaction
region, at which the microstructures having cantilevers exist, to
be within the range from about 600 to 700 degrees centigrade.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] FIG. 1 is a schematic diagram illustrating a basic
configuration of an embodiment of the manufacturing device for
manufacturing carbon nanotube;
[0047] FIG. 2 is a cross sectional view of the vacuum chamber
(i.e., quartz tube) to use in the nanotube manufacturing technique
according to the present this invention;
[0048] FIG. 3 is a schematic perspective view depicting a pair of
microstructures to use in the method for manufacturing carbon
nanotube according to the present invention;
[0049] FIG. 4 is a schematic perspective view showing a part of a
manufacturing device including an array of the reaction regions to
use in the method for manufacturing carbon nanotube according to
the present invention; and
[0050] FIGS. 5A and 5B are schematic block diagrams illustrating an
alternative embodiment of reaction regions to use in the method for
manufacturing carbon nanotube according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] Several preferred embodiments of the present invention will
be described with reference to the accompanying drawings.
[0052] FIG. 1 is a schematic diagram illustrating a basic
configuration of an embodiment of the manufacturing device for
manufacturing carbon nanotube. As shown in FIG. 1, a manufacturing
device comprises: a vacuum chamber (quartz tube) 1 capable of being
optically observed from without; a reaction region 3 (which will be
explained in detail in FIGS. 2 and 3), at which disposed a pair of
cantilevers which are facing each other, in the vacuum chamber 1; a
spot lamp 5 for heating the reaction region to stimulate the growth
of a carbon nanotube; a reactant gas feeding means 7, which is
connected to one end of the vacuum chamber 1, for feeding reactant
gas; a vacuum pump 9, which is connected to other end of the
chamber, for vacuuming the chamber to recover the reactant gas; an
objective lens 11 for observing the generation and growth of a
carbon nanotube; an argon laser 13; an optical filter 15; and a
split photodiode 17.
[0053] The reactant gas feeding means 7 may feed or provide not
only a reactant gas including alcohol vapor (source of carbon),
which mainly consisting of carbon and hydrogen, as a raw material
of nanotubes, but also an argon or hydrogen gas. Non-oxidizing
atmosphere is used to prevent members of the reaction region, such
as cantilevers or carbon nanotube, from alternation or degradation.
When a reactant gas is fed into the vacuum chamber during heating
the reaction region 3, one or more carbon nanotubes start to
generate and grow from a front edge of one cantilever toward a
front edge of other cantilever. When just a carbon nanotube is
connected to the other cantilever, in other words a carbon nanotube
bridge is finished up or built between the two cantilevers, a
position, mechanical properties or optical properties of the both
of either of the cantilever would changes. These changes in
physical properties are measured using a force sensor using one or
more cantilevers (members/elements other than cantilevers are not
illustrated), or a measurement system for measuring minute change
of position utilizing an optical lever method with an optical
system having an argon laser, an optical filter and a split
photodiode. The growth and generation of a carbon nanotube(s) can
be controlled by stopping supply of the reactant gas, or by
increasing the heat of the reaction region to prompt or activate
the growth of the nanotubes.
[0054] FIG. 2 is a cross sectional view of the vacuum chamber
(i.e., quartz tube) to use in the nanotube manufacturing technique
according to the present this invention. Referring to FIG. 2, there
is provided a reaction region 20 for growth a carbon nanotube(s)
and microstructures, i.e., cantilevers 22a and 22b, which are
facing each other, are disposed in the reaction region. The
cantilever 22a is connected to an electrostatic actuator for
vibrating the cantilever. As shown FIG. 2, a change in physical
properties, for example optical vibrations, is measured while
generating the carbon nanotube.
[0055] In this embodiment an optical system for measuring the
optical vibrations (optical lever) is employed. This optical system
mainly includes a laser spot irradiation part 24 for irradiating a
spot of laser light and a measuring part 26 using a split
photodiode. Optionally, there is provided an optical filter and
thus it can be distinguished between the heat ray from the spot
lamp and the laser light from the laser spot irradiation part. The
laser irradiation part 24 can be used as a light source for a Raman
absorption measurement, but additional light source and measurement
device for Raman absorption can be provided.
[0056] According to the number of carbon nanotubes to desire to
measure or generate, a distance between the microstructures and a
mechanical resonance frequency of each microstructure can be
varied. It is preferable to set the sensitivity of a part to low
when the part is a place to want to form a large amount of
nanotubes, and it is preferable to set the sensitivity of a part to
high when the part is a place to want to form or generate a small
amount of nanotubes. It is sufficient that change in physical
properties of either one side of the cantilevers, at which a
nanotube bridge is formed therebetween, can be measured. A
vibration measurement means can be provided in a cantilever, which
is the other side of being bridged. A vibrating means for vibrating
a cantilever(s) from without can be an electrostatic actuator or a
piezoelectric actuator. A piezoelectric actuator 30 applies a
voltage between the cantilever to desire to be vibrated and any
member such as a substrate, and to actuate the cantilever by
electrostatic force. This piezoelectric actuator can be located in
the vacuum chamber or quartz tube. When a vibration field is
provided from without or outside and a cantilever which resonates
with vibrations by the vibration field can be measured, there is no
need to dispose the actuator in the vacuum tube. For example, the
vacuum chamber or quartz tube for reaction can be vibrated outside
the chamber using various frequencies. Each microstructure has one
or more electrodes (not shown in FIG. 2) and an electrical
resistance meter 32 measures a change in resistance using the
electrodes or the electrostatic actuator 30 vibrates or oscillates
the microstructures using the electrodes. It is preferable that the
electrodes are made of only substances, such as titanium or chrome,
which do not have influence on the purification of carbon
nanotubes.
[0057] FIG. 3 is a schematic perspective view depicting a pair of
microstructures to use in the method for manufacturing carbon
nanotube according to the present invention. As shown in FIG. 3,
there is microstructures 40a and 40b having cantilevers 41a and 41b
respectively, in which ends of respective cantilever beams are
facing each other, and the ends or edges of the beams are disposed
in the reaction region. One or more nanotubes are generated or
formed between the cantilevers 41a and 41b. The microstructures 40a
and 40b has a three-layer structure consisting of cantilevers 41a
and 41b, made of silicone, insulation layers 43a and 43b, and
substrates 45a and 45b, which are made of silicone and support the
insulation layers and cantilevers, respectively. In order to be
sensitive to changes of physical properties of the cantilever, the
cantilevers are extremely thinned. In a similar fashion, in order
to increase the sensitive, it is preferable to elongate the beams
of the cantilevers as much as possible. When a voltage is applied
between the cantilever and substrate, the cantilever starts to
vibrate up and down because the cantilever is very thin and this
vibration is measured using various types of sensors during
nanotube generation, and thus the status of the nanotube
manufacture can be grasped appropriately. In this embodiment,
cantilever 41a is kept away from the cantilever 41b by
approximately 5 micrometers and the beam of the cantilever 41a is
vibrated up and down by approximately 1.5 micrometers during
measuring. In addition, the cantilever beam is 170 micrometers in
length, 10 micrometers in width, and 2 micrometer in thickness. The
original values of mechanical physical properties of the lever are
spring constant k=0.7[N/m], resonant frequency f=90 kHz. Although
Shift or change of physical properties varies depending on kind,
characteristics and length of a nanotube when a carbon nanotube
bridge is built or just connected, in this embodiment shift values
per nanotube are approximately .DELTA.k=0.004[N/m] and .DELTA.f=270
Hz and these values can sufficiently be measured using known
various sensors or measurement devices.
[0058] FIG. 4 is a schematic perspective view showing a part of a
manufacturing device including an array of the reaction regions to
use in the method for manufacturing carbon nanotube according to
the present invention. As shown in FIG. 4, a substrate 50 is
processed to provide a plurality of micro flow channels 52a, 52b,
and 52c using the MEMS technology (For convenience, only three flow
channels are illustrated, but actually a great number of micro flow
channels are provided). The micro flow channels are connected to
gas providing means 54a, 54b, and 54c, respectively, which control
a flow rate separately. The micro flow channels have reaction
regions 56a, 56b, and 56c, respectively (which have a plurality of
microstructures, not shown). In addition, there are provided spot
lamps 58a, 58b, and 58c for heating each reaction regions
separately. A desired local part (e.g., only a specific cantilever)
can be locally heated by adjusting focus of a spot of each spot
lamp. They can be an array of lamps or each heating spot lamp
(i.e., its focus point or target area) can be controlled from
outside. Instead of spot lamps, each reaction region has a
resistance unit (not illustrated) to heat its area with resistance
heating. Also, the array of the minute resistor can be used. In
this way, the manufacturing device can be arranged with more than
one micro flow channels like an array and a device for controlling
flow of a reactant gas and heating in each of channel can be
utilized. In the FIG. 4 it is not illustrated but the flow channel
top can be sealed with the transparent quartz panel or the like. In
this connection, the minute flow channels may be an integral
construction having both a substrate to desire to form tubes and
micro flow channels. Alternatively, the flow channel can be another
member, which can be removed from the substrate if tube growth
finished. The gas feeding means may use not only alcohol gas, which
is a main component of the reactant gas, but also various gasses
such as an argon gas, a hydrogen gas, or an oxygen gas. In
addition, there are provided a gas flow rate control means in the
channels, and thus the gas flow rate can be varied or regulated
using these gas flow rate control means depending on measured
changes in physical properties which are obtained during generating
and growing carbon nanotubes.
[0059] FIG. 5A is a schematic block diagram illustrating an
alternative embodiment of reaction regions to use in the method for
manufacturing carbon nanotube according to the present invention.
As shown in FIG. 5A, a reaction region 60 including a plurality of
microstructures are connected to a plurality of minute flow channel
from different directions. These minute flow channels includes
inlets 62a, 62b and 62c for feeding a reactant gas and outlets 64a,
64b and 64c for discharging a gas. Every micro flow channel has one
or more valves. For instance when only a pair of valves, which are
located in the inlet 62a and the outlet 64a respectively, are
opened, a reactant gas flow through the reaction region 60 in one
direction indicated by the arrow at A in FIG. 5. Therefore the gas
flows along with the dotted lines with the arrows in FIG. 5B in one
direction and one or more nanotubes forms along with the flow
direction. Thus one or more carbon nanotube can be formed in a
desired direction. FIG. 5B is an enlarged view of FIG. 5A in that.
As shown in FIG. 5B, the reaction region 60 includes a plurality of
microstructures (group A) in a left side and a plurality of
microstructures (group B) in a right side, which face to the group
B. If gas is fed to the reaction region along with the dotted lines
with arrows, carbon nanotubes are generated and grown along with
the direction of the gas flow (i.e., dotted lines) such as
illustrated carbon nanotubes 66a and 66b. Because the value of the
vibration physical properties of each minute structure depends on
the length of the completed form of a tube (i.e., carbon nanotube
bridge), it is possible to easily and simply grasp in real time
whether or not the desired tube formed in the desired combination
of the microstructures/cantilevers. Also, in a similar principle,
when a plurality of electrodes are disposed around or adjacent to
the reaction region (cantilevers), it is possible to form and grow
carbon nanotubes in a desired direction by adjusting the direction
of applied electric field.
[0060] Further, it should be understood that the detailed
description and specific examples, while indicating preferred
embodiments of the invention, are given by way of illustration
only, not to be used to interpret the scope of the invention.
Various changes and modifications within the spirit and scope of
the invention will become apparent to those skilled in the art from
this detailed description.
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